For efficient use of storage areas in storage systems, there is known a technology of dynamically allocating real storage areas needed for storing data in units called real pages to virtual logical volumes (logical volumes that are virtual) when a write request occurs (refer to PTL 1, for example).
Furthermore, there is known a technology of determining whether or not an I/O request is a request for a storage area of a storage apparatus in receipt of the I/O request and, if the I/O request is a request directed to another storage apparatus, transferring the I/O request to the storage apparatus (refer to PTL 2, for example).
In addition, there is known a technology of embedding a storage area of a pool present in a storage apparatus coupled to another storage apparatus into a storage area of a pool constructed in the latter storage apparatus to allow integration of pools present in multiple storage apparatuses (refer to PTL 3, for example).
According to these technologies, a storages area of one virtual logical volume can be distributed to multiple storage apparatuses, and the storage area of the virtual logical volume can be accessed from any storage apparatus.
Furthermore, there is known a technology of determining whether or not usage of storage apparatuses constituting a tiered pool is optimum as a whole (refer to PTL 4, for example). According to this technology, a migration candidate virtual logical volume and a migration destination pool that are closer to optimum as a whole can be displayed or the virtual logical volume can be migrated.
Furthermore, there is known a technology of efficiently using virtual logical volumes generated on the basis of a tiered pool by different types of applications (refer to PTL 5, for example). According to this technology, the virtual logical volumes can be efficiently used according to the required performance of applications.